The present invention relates generally to multiplexed data buses, and more particularly, to a functional addressing method for use with a multiplexed data bus which employes a single signal to control the operation of systems attached thereto.
In present ground command, control, communications, and intelligence information systems, the traditional hierarchical architecture under control of a central computer results in an inflexible system configuration. A large percentage of the development, procurement, and maintenance costs of such systems are attributable to interface circuitry, cables, and connectors, and the like. Typical system specifications require a system architecture capable of continued operation during the failure and repair of individual units, and during operational reconfiguration of the system. This necessitates an interconnect structure containing no critical nodes or central control elements. These requirments may be met by utilizing an interconnect system employing a data bus which is shared by all units and which comprises a standard bus interface in each unit.
In a conventional large scale system, the interconnection of computers, processors, displays, and peripheral units requires a unique hierarchical arrangement where the function of a unit is determined by its position in the interconnecting topology. Moreover, the associated interfaces of any one type of unit would change, depending on its location in the topology. The conventional system contains a central computer connected to mini-computers through interface units, which in turn communicate with peripherals, displays and communication equipment by way of specialized controllers.
To ensure continuous operation when unit failures occur, the conventional system is redundant, in that a plurality of complete systems are provided to compensate for unit failure. As the number of units in the system increases, the number of point to point interconnections increases at a greater rate and so do the necessary interface units, cards, and cables. The configuration of the interconnecting elements in the topology may vary from system to system, and hence integration of these various systems is most complex.
To circumvent some of the problems associated with this conventional type of system, a single multiplexed data bus may be employed interconnecting each of the units in the system. The central computer may be eliminated by utilizing distributed processing. The computer units are required to interface only with the data bus. Any computer may perform any role in the system since each computer is connected directly to all other computers, peripherals and displays by way of the multiplexed data bus. Continued operation during the failure of a unit only requires an additional backup unit. The result is reduction in the types and numbers of units in the system, and the number of interface cards per unit. As a result, acquisition and life cycle costs are reduced because inventory and maintenance requirements are alleviated.
The routing of messages between units coupled to the data bus is an important design consideration when attempting to arrive at a high-speed data bus. All known prior art data bus designs have employed physical addressing techniques to route messages from unit to unit. This physical addressing procedure requires all originating units on the bus to maintain a logical-to-physical relationship of the entire system. Any change in system role or resources required manual action to reallocate functions to equipment and to set up the new logical-to-physical relationship between all units. Typically, a set of manual switches was used to control the identification of a particular unit, and manual manipulation of the switches was required to modify the logical-to-physical relationship between units.
Thus it would be an advance in the data transmission art to provide a method of functional addressing which eliminates the need for the logical-to-physical relationship between units coupled to a data bus.
It would also be an advance in the data transmission art to provide a method of functional addressing which eliminates the manual switch-setting function to identify units.
It would be a further advance in the data transmission art to provide a method of functional addressing which supports the use of distributed processing concepts applied to a multiplexed data bus that allows for modification of the system configuration at any time.